Climate skeptics have valid reasons to doubt man-made warming

Many people are actively worried about global warming. And it frustrates them that skeptics and “deniers” refuse to acknowledge the “science” of such an urgent, man-made problem.

But there may be valid reasons to dispute the theory that man is responsible for climate change. And to demonstrate why the issue isn’t so clear-cut, here’s a basic climate question to ponder:

As the level of carbon dioxide in the atmosphere increases, does its ability to absorb heat increase, decrease, or remain the same?

Most people will assume the answer is “increase.” After all, CO2 is a “greenhouse” gas. Adding more of it to the atmosphere should mean more heat being “trapped.”

The correct answer, however, is decrease.

How do we know this? Because the UN’s very own, Al Gore-friendly Intergovernmental Panel on Climate Change has acknowledged in its reports that CO2 loses the ability to absorb heat as its concentration increases. The IPCC explains that CO2 follows a “logarithmic dependence,” which means that it takes ever-doubling amounts of CO2 to keep adding the same amount of heat absorption in the atmosphere. In fact, CO2 absorbs only a certain narrow spectrum of infrared radiation, and the IPCC recognizes that the middle of this band is already “saturated.”

People who fret about man-made warming may find it hard to believe that CO2 actually loses “heat trapping” ability. But they should know that even the very climate-concerned IPCC admits to such limitations. They still argue that we need to fear man-made warming, however. And their reason is simply that they believe any additional heat absorbed by CO2 will be greatly amplified by water vapor feedback.

This begs the question … are they right? The answer is “No.”

Water vapor is the primary greenhouse gas of the atmosphere — and responsible for most of the warming that keeps the Earth habitable. In order to make their case, the IPCC theorizes that any additional warming from CO2 will lead to more water vapor in the atmosphere. And this water vapor will trap more heat, raising temperatures further. It is this “feedback loop” that is used to justify their predictions of catastrophic, future warming.

It’s an interesting concept, but it contains an inherent problem. Water vapor added to the atmosphere inevitably transitions to clouds. And cumulus clouds not only reflect solar radiation back into space but also produce rain. And rainfall not only cools surface temperatures but also scrubs CO2 out of the atmosphere. This is why water vapor feedback remains heavily debated in the scientific community, and even the IPCC admits that “an uncertainty range arises from our limited knowledge of clouds and their interactions with radiation.”

One thing we can all agree on, though, is that the Earth has warmed over the past 150 years, and by roughly 0.85 degrees Celsius. But the cause of this warming may well be the significant increase in solar activity during that time. In 2016, Norwegian scientists Harald Yndestad and Jan-Erik Solheim reported that solar output during the 20th century reached the highest levels in 4,000 years. And also in 2016, at least 132 peer-reviewed scientific papers suggested a solar influence on climate.

The IPCC rejects claims of solar variability, though. They argue that changes in solar “irradiance” (brightness) are relatively small. But recent research from scientists like Danish physicist Henrik Svensmark demonstrates that variations in the sun’s output also affect the solar magnetic field and solar wind—which directly influence ionization in the troposphere and cloud formation.

As the IPCC observed in its first assessment report in 1990, global climate in recent millennia “has fluctuated over a range of up to 2 degrees Celsius on time scales of centuries or more.” It’s very possible that the heightened solar activity of the past century has driven recent global warming. As such, there are valid reasons to question the theory of manmade climate change, and to urge greater study of the issue.

Dave Rothbard is president and Craig Rucker is executive director of CFACT, a Washington, DC-based public-policy organization founded in 1985.